freeswitch/libs/srtp/crypto/cipher/aes_icm_mbedtls.c

/*
 * aes_icm_mbedtls.c
 *
 * AES Integer Counter Mode
 *
 * YongCheng Yang
 */

/*
 *
 * Copyright (c) 2013-2017, Cisco Systems, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 *   Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 *   Neither the name of the Cisco Systems, Inc. nor the names of its
 *   contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <mbedtls/aes.h>
#include "aes_icm_ext.h"
#include "crypto_types.h"
#include "err.h" /* for srtp_debug */
#include "alloc.h"
#include "cipher_types.h"
#include "cipher_test_cases.h"

srtp_debug_module_t srtp_mod_aes_icm = {
    0,                /* debugging is off by default */
    "aes icm mbedtls" /* printable module name       */
};

/*
 * integer counter mode works as follows:
 *
 * https://tools.ietf.org/html/rfc3711#section-4.1.1
 *
 * E(k, IV) || E(k, IV + 1 mod 2^128) || E(k, IV + 2 mod 2^128) ...
 * IV = (k_s * 2^16) XOR (SSRC * 2^64) XOR (i * 2^16)
 *
 * IV SHALL be defined by the SSRC, the SRTP packet index i,
 * and the SRTP session salting key k_s.
 *
 * SSRC: 32bits.
 * Sequence number: 16bits.
 * nonce is 64bits. .
 * packet index = ROC || SEQ. (ROC: Rollover counter)
 *
 * 16 bits
 * <----->
 * +------+------+------+------+------+------+------+------+
 * |           nonce           |    packet index    |  ctr |---+
 * +------+------+------+------+------+------+------+------+   |
 *                                                             |
 * +------+------+------+------+------+------+------+------+   v
 * |                      salt                      |000000|->(+)
 * +------+------+------+------+------+------+------+------+   |
 *                                                             |
 *                                                        +---------+
 *                                                        | encrypt |
 *                                                        +---------+
 *                                                             |
 * +------+------+------+------+------+------+------+------+   |
 * |                    keystream block                    |<--+
 * +------+------+------+------+------+------+------+------+
 *
 * All fields are big-endian
 *
 * ctr is the block counter, which increments from zero for
 * each packet (16 bits wide)
 *
 * packet index is distinct for each packet (48 bits wide)
 *
 * nonce can be distinct across many uses of the same key, or
 * can be a fixed value per key, or can be per-packet randomness
 * (64 bits)
 *
 */

/*
 * This function allocates a new instance of this crypto engine.
 * The key_len parameter should be one of 30, 38, or 46 for
 * AES-128, AES-192, and AES-256 respectively.  Note, this key_len
 * value is inflated, as it also accounts for the 112 bit salt
 * value.  The tlen argument is for the AEAD tag length, which
 * isn't used in counter mode.
 */
static srtp_err_status_t srtp_aes_icm_mbedtls_alloc(srtp_cipher_t **c,
                                                    int key_len,
                                                    int tlen)
{
    srtp_aes_icm_ctx_t *icm;

    debug_print(srtp_mod_aes_icm, "allocating cipher with key length %d",
                key_len);

    /*
     * Verify the key_len is valid for one of: AES-128/192/256
     */
    if (key_len != SRTP_AES_ICM_128_KEY_LEN_WSALT &&
        key_len != SRTP_AES_ICM_192_KEY_LEN_WSALT &&
        key_len != SRTP_AES_ICM_256_KEY_LEN_WSALT) {
        return srtp_err_status_bad_param;
    }

    /* allocate memory a cipher of type aes_icm */
    *c = (srtp_cipher_t *)srtp_crypto_alloc(sizeof(srtp_cipher_t));
    if (*c == NULL) {
        return srtp_err_status_alloc_fail;
    }

    icm = (srtp_aes_icm_ctx_t *)srtp_crypto_alloc(sizeof(srtp_aes_icm_ctx_t));
    if (icm == NULL) {
        srtp_crypto_free(*c);
        *c = NULL;
        return srtp_err_status_alloc_fail;
    }

    icm->ctx =
        (mbedtls_aes_context *)srtp_crypto_alloc(sizeof(mbedtls_aes_context));
    if (icm->ctx == NULL) {
        srtp_crypto_free(icm);
        srtp_crypto_free(*c);
        *c = NULL;
        return srtp_err_status_alloc_fail;
    }

    mbedtls_aes_init(icm->ctx);

    /* set pointers */
    (*c)->state = icm;

    /* setup cipher parameters */
    switch (key_len) {
    case SRTP_AES_ICM_128_KEY_LEN_WSALT:
        (*c)->algorithm = SRTP_AES_ICM_128;
        (*c)->type = &srtp_aes_icm_128;
        icm->key_size = SRTP_AES_128_KEY_LEN;
        break;
    case SRTP_AES_ICM_192_KEY_LEN_WSALT:
        (*c)->algorithm = SRTP_AES_ICM_192;
        (*c)->type = &srtp_aes_icm_192;
        icm->key_size = SRTP_AES_192_KEY_LEN;
        break;
    case SRTP_AES_ICM_256_KEY_LEN_WSALT:
        (*c)->algorithm = SRTP_AES_ICM_256;
        (*c)->type = &srtp_aes_icm_256;
        icm->key_size = SRTP_AES_256_KEY_LEN;
        break;
    }

    /* set key size        */
    (*c)->key_len = key_len;

    return srtp_err_status_ok;
}

/*
 * This function deallocates an instance of this engine
 */
static srtp_err_status_t srtp_aes_icm_mbedtls_dealloc(srtp_cipher_t *c)
{
    srtp_aes_icm_ctx_t *ctx;

    if (c == NULL) {
        return srtp_err_status_bad_param;
    }

    /*
     * Free the aes context
     */
    ctx = (srtp_aes_icm_ctx_t *)c->state;
    if (ctx != NULL) {
        mbedtls_aes_free(ctx->ctx);
        srtp_crypto_free(ctx->ctx);
        /* zeroize the key material */
        octet_string_set_to_zero(ctx, sizeof(srtp_aes_icm_ctx_t));
        srtp_crypto_free(ctx);
    }

    /* free memory */
    srtp_crypto_free(c);

    return srtp_err_status_ok;
}

static srtp_err_status_t srtp_aes_icm_mbedtls_context_init(void *cv,
                                                           const uint8_t *key)
{
    srtp_aes_icm_ctx_t *c = (srtp_aes_icm_ctx_t *)cv;
    uint32_t key_size_in_bits = (c->key_size << 3);
    int errcode = 0;

    /*
     * set counter and initial values to 'offset' value, being careful not to
     * go past the end of the key buffer
     */
    v128_set_to_zero(&c->counter);
    v128_set_to_zero(&c->offset);
    memcpy(&c->counter, key + c->key_size, SRTP_SALT_LEN);
    memcpy(&c->offset, key + c->key_size, SRTP_SALT_LEN);

    /* force last two octets of the offset to zero (for srtp compatibility) */
    c->offset.v8[SRTP_SALT_LEN] = c->offset.v8[SRTP_SALT_LEN + 1] = 0;
    c->counter.v8[SRTP_SALT_LEN] = c->counter.v8[SRTP_SALT_LEN + 1] = 0;
    debug_print(srtp_mod_aes_icm, "key:  %s",
                srtp_octet_string_hex_string(key, c->key_size));
    debug_print(srtp_mod_aes_icm, "offset: %s", v128_hex_string(&c->offset));

    switch (c->key_size) {
    case SRTP_AES_256_KEY_LEN:
    case SRTP_AES_192_KEY_LEN:
    case SRTP_AES_128_KEY_LEN:
        break;
    default:
        return srtp_err_status_bad_param;
        break;
    }

    errcode = mbedtls_aes_setkey_enc(c->ctx, key, key_size_in_bits);
    if (errcode != 0) {
        debug_print(srtp_mod_aes_icm, "errCode: %d", errcode);
    }

    return srtp_err_status_ok;
}

/*
 * aes_icm_set_iv(c, iv) sets the counter value to the exor of iv with
 * the offset
 */
static srtp_err_status_t srtp_aes_icm_mbedtls_set_iv(
    void *cv,
    uint8_t *iv,
    srtp_cipher_direction_t dir)
{
    srtp_aes_icm_ctx_t *c = (srtp_aes_icm_ctx_t *)cv;
    v128_t nonce;
    c->nc_off = 0;
    /* set nonce (for alignment) */
    v128_copy_octet_string(&nonce, iv);

    debug_print(srtp_mod_aes_icm, "setting iv: %s", v128_hex_string(&nonce));

    v128_xor(&c->counter, &c->offset, &nonce);

    debug_print(srtp_mod_aes_icm, "set_counter: %s",
                v128_hex_string(&c->counter));

    return srtp_err_status_ok;
}

/*
 * This function encrypts a buffer using AES CTR mode
 *
 * Parameters:
 *	c	Crypto context
 *	buf	data to encrypt
 *	enc_len	length of encrypt buffer
 */
static srtp_err_status_t srtp_aes_icm_mbedtls_encrypt(void *cv,
                                                      unsigned char *buf,
                                                      unsigned int *enc_len)
{
    srtp_aes_icm_ctx_t *c = (srtp_aes_icm_ctx_t *)cv;

    int errCode = 0;
    debug_print(srtp_mod_aes_icm, "rs0: %s", v128_hex_string(&c->counter));

    errCode =
        mbedtls_aes_crypt_ctr(c->ctx, *enc_len, &(c->nc_off), c->counter.v8,
                              c->stream_block.v8, buf, buf);
    if (errCode != 0) {
        debug_print(srtp_mod_aes_icm, "encrypt error: %d", errCode);
        return srtp_err_status_cipher_fail;
    }

    return srtp_err_status_ok;
}

/*
 * Name of this crypto engine
 */
static const char srtp_aes_icm_128_mbedtls_description[] =
    "AES-128 counter mode using mbedtls";
static const char srtp_aes_icm_192_mbedtls_description[] =
    "AES-192 counter mode using mbedtls";
static const char srtp_aes_icm_256_mbedtls_description[] =
    "AES-256 counter mode using mbedtls";

/*
 * This is the function table for this crypto engine.
 * note: the encrypt function is identical to the decrypt function
 */
const srtp_cipher_type_t srtp_aes_icm_128 = {
    srtp_aes_icm_mbedtls_alloc,           /* */
    srtp_aes_icm_mbedtls_dealloc,         /* */
    srtp_aes_icm_mbedtls_context_init,    /* */
    0,                                    /* set_aad */
    srtp_aes_icm_mbedtls_encrypt,         /* */
    srtp_aes_icm_mbedtls_encrypt,         /* */
    srtp_aes_icm_mbedtls_set_iv,          /* */
    0,                                    /* get_tag */
    srtp_aes_icm_128_mbedtls_description, /* */
    &srtp_aes_icm_128_test_case_0,        /* */
    SRTP_AES_ICM_128                      /* */
};

/*
 * This is the function table for this crypto engine.
 * note: the encrypt function is identical to the decrypt function
 */
const srtp_cipher_type_t srtp_aes_icm_192 = {
    srtp_aes_icm_mbedtls_alloc,           /* */
    srtp_aes_icm_mbedtls_dealloc,         /* */
    srtp_aes_icm_mbedtls_context_init,    /* */
    0,                                    /* set_aad */
    srtp_aes_icm_mbedtls_encrypt,         /* */
    srtp_aes_icm_mbedtls_encrypt,         /* */
    srtp_aes_icm_mbedtls_set_iv,          /* */
    0,                                    /* get_tag */
    srtp_aes_icm_192_mbedtls_description, /* */
    &srtp_aes_icm_192_test_case_0,        /* */
    SRTP_AES_ICM_192                      /* */
};

/*
 * This is the function table for this crypto engine.
 * note: the encrypt function is identical to the decrypt function
 */
const srtp_cipher_type_t srtp_aes_icm_256 = {
    srtp_aes_icm_mbedtls_alloc,           /* */
    srtp_aes_icm_mbedtls_dealloc,         /* */
    srtp_aes_icm_mbedtls_context_init,    /* */
    0,                                    /* set_aad */
    srtp_aes_icm_mbedtls_encrypt,         /* */
    srtp_aes_icm_mbedtls_encrypt,         /* */
    srtp_aes_icm_mbedtls_set_iv,          /* */
    0,                                    /* get_tag */
    srtp_aes_icm_256_mbedtls_description, /* */
    &srtp_aes_icm_256_test_case_0,        /* */
    SRTP_AES_ICM_256                      /* */
};